OT: Inter-Aural Phase Cancellation?

[lindsay@pavestone.com]

I recently recorded six improvisational comedians in an audio-only setting,
but stumbled into a strange phenomenon.  Each performer had their own mic,
running into their own channel on the board, mixed down to stereo
two-track, through a limiter, then to a stand-alone CDR, then to a
distribution amp, and then to six pair of headphones.

What happened was this: each performer complained that there own voice was
low in volume compared to the others in the mix.  As everyone was listening
to the same mix, I found that a bit odd, but indeed when I spoke into the
mic whilst everyone else spoke too, my voice did seem decidedly lower in
volume.  I could watch meters all day, making sure the levels were even,
but still it really did sound like your own voice was significantly lower
in the mix.

Now, I have a few theories about this, but I'd love to hear what you guys
think.  Is it possible that the signal coming from the headphones is out of
phase with the sound of your own voice inside your head?  Are they
cancelling each other out?  Or is this just a psycho-acoustic effect,
whereby you are trained to ignore your own voice and thereby hear it
differently when presented the sound in this context.

As it was, everyone did fine--it did not affect the performance, but still,
it was strange.  Any thoughts?